Molecular Crystals and Liquid Crystals, Vol.394, 127-139, 2003
2H and N-14 NMR of cetylpyridinium bromide lyotropic and thermotropic liquid crystals
H-2 and N-14 NMR spectra of the cationic head group have been recorded for liquid crystalline systems of CPB (cetylpyridinium bromide), pentanol and NaBr brine, at low surfactant content. The H-2 quadrupolar splittings provided the order parameters of the aromatic ring at various temperatures. Using these order parameters, the experimentally determined N-14 quadrupolar splittings allowed the evaluation of the principal values of the nitrogen quadrupole coupling tensor, \C-Q\ = 0.41 MHz and eta = 0.39. H-2 quadrupolar splittings measured for the thermotropic liquid crystal given by pure CPB above 71degreesC allowed to calculate the ring order parameters also for this phase. These parameters and the N-14 \ C-Q\ and eta values led to N-14 splitting values in very good agreement with those actually observed for this thermotropic ionic liquid crystal.
Keywords:H-2 NMR;N-14 NMR;cetylpyridinium bromide;swollen lamellar phase;thermotropic ionic liquid crystal;N-14 quadrupole coupling